The present invention relates to a device that regulates an outlet valve on a self-discharging centrifugal drum, the outlet valve being the type which diverts closure fluid from a closure compartment having a piston valve which delimits a solids space and moves from a closure position while the solids space is being partly or completely emptied. The device has an operating-fluid line with a shutoff, which is connected to a set of controls and which diverts the operating fluid through an annular channel in the shell of the drum and through one or more supply channels to the outlet valve, and has a supply line, which supplies closure fluid to the closure compartment.
Such a device on a self-discharging centrifugal drum, wherein a certain volume of operating fluid is subjected to a certain degree of pressure and supplied to an outlet valve that operates under centrifugal force when the drum empties partly or completely, is known for example from German Pat. No. 2 048 429.
When the drum empties, the solid components of the centrifuged material that accumulate in the solids space must be ejected as rapidly as possible. Whether all of these solids can be ejected uniformly depends on the speed of the axially displaceable piston valve in the drum. At a constant volume of ejection, the more rapidly the piston valve moves into its lower position the larger the gap that opens to permit the solids to be ejected.
Since the amount of solids to be ejected, the drum packing, varies in accordance with whether the drum is discharging partly or completely, the piston valve must either be controlled from outside by timers with the appropriate volume of operating fluid being determined by its existing pressure, or the drum must be provided with a very expensive hydraulics system with, for example, several closure compartments.
In known systems, which are controlled from outside, compromises have always had to be made up to now with respect to piston-valve speed. If the drum was designed for extremely rapid complete discharge, it was extremely difficult to employ timers to achieve precise partial discharge because the discharge periods were too short. The ratio became more deleterious, the larger the separator drum. Another, and major, drawback of time-based control is its dependence on operating-fluid pressure and on any inertia in the operating-fluid shutoffs. If, that is, it is desired that the volume of solids ejected remain constant during the whole operation and with a long opening stroke, very rapid opening in other words, it will not be possible to control the process with timers alone. Such drums can be controlled only by automatic closure with restriction piston valves integrated into the drum. Drawbacks of this type of control are its expense and the impossibility of regulating the volume of solids ejected from outside.